Light-sensitive silver halide emulsions and process of manufacturing the same



6 same and to a process for manufacturing the Patent ed May 13, 1930 UNITEDTSTVATES PATENT OFFICE OTTO MATTHIES AND BRUNO WENDT, OF DESSAU IN ANHALT, GERMANY, ASSI GNORS TO AGFA ANSOO CORPORATION, OF IBINGHAMTON, NEW YORK, A CORPORATION OF NEWYORK,

LIGHT-SENSITIVE SILVER nnmnn nMULsIoNs AND PROCESS or mnnurno'runmq .THE SAME No Drawing. Application filed January 28, 1929, Serial No. 835,783, and in Germany January 81, 1928.-

The present invention relates to photo graphic silver salt emulsions of increased stability, little tendency to fog and determined grain size, to layers containing the same. K

We found that all organic nitrogen compounds with three or more nitrogen atoms 1n the molecule containing at least one ==NH 10 group, the H atom of which is liable to sublessen the tendency to fog of light sensitive silver halide emulsions on being added to the finished emulsion or to any of its constituents during manufacture. The compounds which form silver salts of the least solubility exert the strongest effect .on the stability of emul sions.

It has furthermore been found that the said com ounds when present during the addition of the silver nitrate solution restrain the growing of silver bromide grains and thus give to the emulsion a steeper gradation while in the same time increasing its stabilit By our present process we may thus 0 tain emulsions of varying steepness of gradation though starting with the same proportions of constituents. The said addition may be made to the finished-emulsion or to its constituents at any stage of its manufacture or of emulsion making.

The following examplesillustrate' the invention:

Example 1.-In a prescription for the manufacture of a highly sensitive negative-emulsion with use of a gelatine which produces fog, there is added to the gelatine, while itis being digested, 50 milligrams of tetrazole per 100 grams of silver nitrate. There is obtained a highly sensitive, clear emulsion.

Example Q.A highly sensitive negative emulsion is made according to any known prescription and before the silver salt solution is run into the potassium bromide solution there are added to the latter 7O milligrams of 5-methylbenzotriazole per each 100 grams of silver nitrate. There is thus obtained a-clear emulsion of finer grain than when made without the addition of 5-methylbenzotriazole. Y

\Ve claim: 1. A process of manufacturing light sensitivesilver halide emulsions of increased stability, in which there is added to the emulsion a compound forming a stable silver salt of no higher solubility than silver chloride and containing at least 3 nitrogen atoms in the molecule at least one of which being linked to a hydrogen atom which is liable to substitution by silver. v

2. A process of manufacturing light sensitive silver halide emulsions of increased stability, in which there is added to a constituent of the emulsion at any stage of the manufacture a compound forming a stable silver salt of no higher solubility than silver chloride and containing at least 3 nitrogen atoms in the molecule at least one of which being linked to a hydrogen atom which is liable to substitution by silver.

3. A process of manufacturing light sensi tive silver halide emulsions of increased stability and restrained size of silver halide grains, in which there is added to a constitu-1 ent of the emulsion prior to the addition of silver nitrate a compound forming a stable silver salt of no higher solubility than silver chloride and containing at least 3 nitrogen atoms in the molecule at least one of which being linked to a hydrogen atom which is liable to substitution by silver.

4;. A process of manufacturing light sensitive silver halide emulsions of increased stability, in which there is added to the emulsion a compound forming a stable silver salt of no higher solubility than silver chlo ride and containing 3 nitrogen atoms in the molecule at least one of which being linked to a hydrogen atom which is liable to substitution by silver.

5. A process of manufacturing light sensitive silver halide ei'nulsions of increased stability, in which there is added toa constituent of the emulsion at any stage of the manufacture a compound forming a stable silver salt of no higher solubility'than silver chloride and containing 3 nitrogen atoms in the molecule at least one of which being linked to a hydrogen atom which isliable to substitution by silver. 7

6. A process of manufacturing light sen sitive silver halide emulsions of increased stability and restrained size of silvergrains, in which there is added to a constituent of the emulsion prior to the addition of-silver nitrate a compound forming a stable silver salt of no higher solubility than silver chloride and containing 3 nitrogen atoms in the molecule at least one of which being linked to a hydrogen atom which is liable to substitution by silver.

7. Light sensitive silver halide emulsions containing a compound forming a stable silver salt of no higher solubility than silver chloride and containing at least 3 nitrogen atoms in the molecule at least one of which being linked to a hydrogen atom which is liable to substitution by silver.

8. Light sensitive silver halide emulsions containing a compound forming a stable silver salt of no higher solubility than silver chloride and containing 3 nitrogen atoms in the molecule at least one of which being linked to a hydrogen atom which is liable to substitution by silver.

9. A process of'manufacturing light sensitive silver halide emulsions of increased stability ipmprising the step of adding tetrazole.

10. sitive silver halide emulsions of increased stability comprising the step of adding tetrazole to a constituent of the emulsion at any stage of its manufacture. a

11. Light sensitive silver halide emulsions containin tetrazole.

12. Lig t sensitive silver halide emulsions containing tetrazole added to a constituent of the emuls'on at any stage of its manufacture.

In testimony whereof, we afiix our signatures.

OTTO MATTHIES. BRUNO WEN DT.

process of manufacturing light sen-- 

